1. Field of the Invention
The present invention relates a method of forming a device isolation film in a semiconductor device. More particularly, the present invention relates to a method of forming a device isolation film in a semiconductor device which prevents gaps and voids from forming in the device isolation film of the semiconductor device.
2. Discussion of the Related Art
In highly integrated semiconductor devices with less than 90 nm processes, the width of the gates and the width of the transistor is so narrow that the depth of the trenches are deeper than the depth at a junction the source and drain so as to electrically isolate the areas in the devices.
One method of electrically isolating the areas in the semiconductor devices known in the art is the local oxidation of silicon (LOCOS) method, wherein the silicon substrate is recessed and an insulating layer is grown wherein a shallow trench isolation method is used to etch the silicon substrate in a vertical direction and cover it with the insulating material.
FIG. 1 is a cross-sectional view illustrating the LOCOS method for forming a device isolation film of a semiconductor device according to the related art. As shown in FIG. 1, an insulating layer is formed on a semiconductor substrate. Next, a photoresist pattern is formed on the insulating layer by coating a photoresist material. Then, an etching process is performed using the photoresist pattern to form a series of trenches in the semiconductor substrate. Later, an ashing and cleaning process is performed to remove the photoresist pattern and the trench is filled by depositing the insulating layer over the semiconductor substrate and the trench. Then, a planarization process is performed using a chemical mechanical polishing (CMP) method in order to form a shallow trench isolation (STI).
One difficulty in the process, however, illustrated in FIG. 1, is that the upper corners (A) of the trenches in the semiconductor device are narrow, making it difficult to successfully form the insulating layer with a high density plasma chemical vapor deposition (HDPCVD) apparatus without forming gaps or voids in the insulating layer formed in the trenches.